Board Joints

When skimming over plasterboard joints (scrimmed) I sometimes find they firm up sooner than the rest of the wall and leave me with visible ridges after final trowel. I'm guessing this is due to increased suction from board edges?Any tips/advice?Thanks!

AnswerIt is often the opposite case - that they stay a bit softer and so when final trowelling takes place they may not be fully firm and therefore just sag out a bit and are not flattened. If they tend to firm up quicker - it is easily resolved by applying more pressure to ensure they get flattened off properly!

If there is a ridge at any stage then take extra time to flatten. If it does not flatten due to being soft then just keep returning. Ultimately they will definitely flatten just before it all finally sets, so as the plaster begins to change colour due to the set taking place - flatten any areas that may need it!